Fire extinguisher



Oct. 5, 1948. N. J. THOMPSON FIRE EXTINGUISHER Filed June 28, 1946 [ZZZ/m7 A brwzarp 17720 01:

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Patented Dot. 5, 1948 UNITED" STATES PATENT OFFICE FIRE EXTINGUISHER Norman J. Thompson, Newton, Mass, assignor to FactoryMutual Research Corporation, Boston, Mass., a corporation of Massachusetts Application June 28, 1946, Serial No. 680,261

2 Claims.

This invention relates to fire extinguishers and more particularly to a bomb-type extinguisher adapted to disperse and distribute a fire-extinguishing agent for extinguishing or preventing the development and propagation of a, fire.

The primary object of my invention is to provide a fire extinguisher of the character described which will cause a more efiective and efiicient explosive dispersion and distribution of a fire-extinguishing agent than has heretofore been ac-' complished. Another object is to provide a fire extinguisher of the type described which is thoroughly safe in installation and use, which will result in no personal injury and which may be installed in ducts, vents or other small chambers without danger of structural damage thereto. A further object of my invention is to provide an apparatus of the character described which is thoroughly reliable in operation over long periods of time and which is not affected by normal variations in atmospheric humidity or normal vibrations customarily experienced in factories,

shops, or conveyances. Still another object is to provide a fire extinguisher of the character described which is suitable for effective application in'locations entirely inaccessible for manual application of ordinary extinguishing agents as, for example, in an enclosed pneumatic conveying system, to provide a non-combustible condition in advance of a fire in swiftly moving airborne material. Another object is to provide an apparatus which is adapted to utilize any effective fire-extinguishing agent whether in powder or liquid form and which may be utilized to extinguish fires in all types of combustible materials including inflammable liquids. Other objects of my invention are to provide an extinguisher of the type described which is economical to manufacture and use, simple to manufacture, install and maintain and readily adaptable to bombs which may:

be of odd or peculiar shape because of limited or restricted space requirements.

In one aspect my invention involves a fire extinguisher comprising a frangible casing, a fireextlnguishing agent within the casing, a 'fiexible explosive cord looped back and forth upon itself within the body of the agent and means within the casing for detonating the explosive cord. In a preferred aspect the cord consists of a high velocity, sharp acting explosive adapted to create a high interior pressure of instantaneous duration within the casing, and the cord being free of noncombustible material. In another aspect the fire extinguisher comprises a frangible container, a fire-extinguishing agent within the container,

2 and an explosive resistant casing formed with an opening and disposed within the body of the agent and a flexible explosive cord. wound exteriorly about and supported by the casing and comprising an extension through the opening into said casing and means Within the casing for detonating the explosive cord. In a preferred-aspect the fire-extinguishing agent is in powder form and the explosive cord may either be looped back and forth upon itself and embedded in the body of the agent or the explosive resistant casing supporting the cord may be embedded in the body oi the'agent. The detonating means is a detonating charge within the casing and in the preferred aspect is responsive to the passage of electric current for detonating the explosive cord. Further, in the preferred aspect, the detonating means is a detonator within the explosive-resistant casing contiguous to the extension of the flexible explosive cord and responsive to the passage of electric current for detonating the cord, the 'fragments of the detonator being retained within the casing on detonation. I

For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawing in which the single figure is a vertical section.

Referring to the drawings, the numeral I represents a cylindrical container having a bottom 2 and side wall 3 of frangible material, preferably of moisture-proof paper. An annular container top 4 of a strong explosive-resistant material, as for example steel, has an inner flange 5 and an outer flange 6, the inner flange being threaded to receive a bushing 1. The top portion of the side wall 3 is secured to the container top 4 by suitable means as a retaining ring 8 wedging said top portion of the side wall against the outer flange 6 of the container top.

The bushing l is formed with a threaded axial bore 9 which is enlarged at its inner end to threadably receive one end of a tubular member ID of explosive-resistant material, as for example steel, the tubular member extending inwardly and centrally into the container I, as shownin the drawing. A plug I l is threaded into the outer end of the bore of the bushing 1 and is providedwith an externally threaded extension l2 projecting through an opening I3 in a standard junction box M, the junction box being removably secured to the extension l2 by a lock nut I-5.

The plug I l is formed with an axial bore I 6 which is enlarged at its inner end to receive the base of a detonator H, the detonator preferably consisting of a No. 6 electrically actuated blasting cap and extending axially into the tubular casing ID. A plug [8 is threaded into the opposite end of the tubular casing l and is formed with an axial bore 19 which is enlarged at its inner end to receive and support one end of a tube member 20. The tube member 20 extends axially into the tubular casing Hi, the opposite end of said tubular member entering one end of the 'bore of a spider 2| and providing a support for said spider within the casing ID. The opposite end of the bore of the spider 2| receives, with a pressed fit, the open end 22 of the detonator l1.

A flexible explosive cord 23, having one end contiguous with the open end 22 of the detonator l1, extends through the tube member 20 where it v is snugly held in fixed position, and thence extends out of tubular casing l0 through the ,plug l8 and thence winds about the outside of the casing ID, as shown in the drawing.

The flexible explosive cord 23 preferably con sists of a flexible moisture-proof casing 24 free of any non-combustible material, the interior of the-casing being filled with a rapid-burning highvelocity, sharp-actuating type of explosive 25 adapted to create a high interior pressure of instantaneous duration within the container 1. An example of the type of explosive possessing the characteristics disclosed is pentaerithrytol tetranitrate.

The interior of the casing I exclusive of the space occupied by the tubular casing l0 and the explosive cord '23 disposed outside of said casing is filled with any Well-known effective fire extinguishing agent 26 preferably in powder form as for example Dugas the tubular casing I0 and the explosive cord disposed outside of said casing being embedded Within said agent.

One end of an electric conduit 21 is threadably received through an opening '28 in the junction box 1-4, and wires 29, connected at one end to a source of electricity (not shown), extend through said conduit into the junction box and thence through the apertured plug I l where they are joined to the base of the detonator 11. It is to be understood that the electric conduit 21 is of sufficient strength to support the weight of the assembled apparatus when filled with a fire extinguishing agent and, therefore, provides a means for mounting the apparatus on any convenient surface, as for example a ceiling by seaotuated electrical switch located in proximity to a firing area or may be manually and remotely actuated at will by a push button switch or the like, but, in either case, energizing of the wires leading to the detonator I! will cause the detonator to explode into the contiguous end of the flexible cord 23 which in turn will instantaneously explode the entire flexible cord 23. The high interior pressure of instantaneous duration created by the explosion of the cord within the container I and outside the casing II] will be sufiicient to force the fire extinguishing agent outwardly against the bottom and side Walls of the container causing them to burst, thereby permitting the agent to be dispersed and distributed over the fire or threatened fire area to extinguish or prevent the spread or propagation of a fire.

It will be noted that because of the explosivevided but, because of the instantaneous duration of the explosive blast, no structural damage or injury results to the material surrounding the apparatus.

It is further evident from the above that the device is suitable for distribution of any efiective fire extinguishing agent whether in powder or liquid form and may be utilized wherever a similar type of dispersion or distribution of a liquid or powder is required. It is to be noted also that the flexible explosive @cord used need not necessarily be supported or wound about the tubular casing, but may be distributed throughout the body of the agent wherever it is most effective, depending upon the shape of the frangible container, as for example along the longitudinal axis of arm-elongate container.

It should be understood that the present disclosure is for the purpose of illustration only and that thisinvention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. A fire extinguisher comprising a frangible container, a fire-extinguishing agent within the container, an explosive resistant casing formed with an opening-and disposed within the agent a flexible explosive cord wound exteriorly about and supported by the casing and comprising an extension through the opening into said casing, a detonator within the casing and contigous to said extension responsive to the passage of electric current for detonating the cord, the fragmentsof the detonator being retained within the casing on detonation.

2. A fire extinguisher comprising a frangible container, a fire-extinguishing agent in powder form within the container, an explosive resistant casing formed withan opening and embedded within the agent, a flexible cord wound exteriorly about and supported by the casing and comprising an extension through the opening into the casing, the cord consisting of a high velocity, sharp acting explosive adapted to create a high interior pressure of instantaneous duration within the container and the cord being free of noncombustible material, and a detonator within the casing and contiguous to said extension responsive to the passage of electric current for detonating the cord, the fragments of the detonator being retained within the casing on detonation.

NORMAN J. THOMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 750,416 Walrath Jan. 26, 1904 1,211,919 Cock Jan. 9, 1917 1,648,397 Hermann Nov. 8, 1927 

